1. Field of the Invention
The present invention relates to the field of information recording equipment, and particularly to equipment for recording on a medium such as tape information derived from a keyboard input such as a stenographic machine keyboard.
2. Prior Art
In many situations, there is a need to record conversations and the like and to provide a printed copy thereof at both a high speed and with high accuracy in content. While the desired final product may readily be produced by a conventional typewriter, the speed of even the best typist is not sufficient to record the spoken words at normal speech rates. Therefore, some intermediate recording technique and medium is generally utilized to record the spoken word in some form which later is transcribed to provide the desired printed finished product.
In many situations, the spoken word is recorded by a stenographer using some form of shorthand, and later transcribed by the stenographer to the desired end product. Differences in shorthand techniques however, may make it difficult or impossible for one person to read another person's shorthand so that the shorthand record may be of little lasting value. In other situations, the spoken word is directly recorded on magnetic tape for later playback and transcription. In ideal situations, such a technique is highly satisfactory, as background noise, etc. may be controlled, the voices are generally known, and questions may be asked wherever the taped information is unclear. However, in other situations, such as by way of example, in a typical court reporting atmosphere, whether in depositions or actual court room recording, this technique has been found to be unsatisfactory for various reasons. For instance, in some situations the information thought to be taken is masked by background noises, different voices are sometimes not readily distinguishable so that the speaker cannot be later identified; malfunction of the equipment is not always visually apparent, etc. Accordingly, the steno machine is substantially universally used for this type of recording. Such a machine utilizes a keyboard of a predetermined number of characters which, in various combinations, may be used to provide a phonetic recording of the spoken word for later transcription. Such a machine typically provides a printout on paper providing a permanent record which is immediately reviewable to insure proper recording and which in general may be transcribed by someone other than the person doing the recording.
It would be highly desirable to provide a means for automatic transcription of the steno recording so that preferably a finished printed output could be immediately and quickly derived, or a printed output having a minimum number of grammatical errors could be quickly produced, which then could be read and corrected in minimum time by the reporter. Computer programs for transcribing the recorded information, which typically is a phonetic representation of the spoken word, are presently known and are currently the subject of considerable effort for the improvement thereof. Also, various devices and systems are known for converting the key depression into electrical signals which may be recorded and placed in compatible form for input to a computer programmed to transcribe the information. It is such a system that the present invention is directed.
Prior art systems for providing an electrical signal in response to key depression utilize variable inductance devices and switching devices. The variable inductance devices have generally been comprised of a stationery wound magnetic member disposed adjacent to a portion of a respective key so that the inductance of the device is affected by the relative location of the key. Such devices depend upon the magnetic characteristics of the key, and other parameters which otherwise are of no interest to the manufacturer of the steno machine, so that performance of the variable inductance sensor may be limited and have to be matched to the magnetic characteristices of the key. Also, such systems as are noted in the prior art, have utilized RL circuits, which circuits are not the most sensitive to provide a high level output. Other systems have used variable inductors as a frequency determining component in an oscillator circuit, so that the frequency of oscillation is responsive to key depression. These systems generally provide for detection by a low pass filter, with the sensitivity of the system being determining by the amount of frequency shift and by the sharpness of the cutoff of the low pass filter. Since one entire circuit is required for each key, the overall system is rather complex and expensive, and may be quite sensitive to the proper adjustment of the various components. Prior art systems utilizing mechanical switches, of course, provide the desired information but are subject to the well known problems of switches, including contamination, oxidation, noise, mechanical failure, etc.
An ideal key position sensing system is a system which is relatively simple and inexpensive to fabricate, which provides high level output signals, and which may be separately fabricated and installed into existing and new steno machines without substantial alteration thereof and without special requirements in such machines.